void main() {
  Map map = {'name': '张三', 'age': 18};
  print(map);
  print(map['name']);
  map['name'] = '李四';
  print(map['name']);
  map.forEach((key, value) {
    print('$key:$value');
  });

  map.addAll({'sex': '男'});
  print(map);
  print(map.containsKey('sex'));

  map.remove('age');
  print(map);

  map.clear();
  print(map);   

}